This disclosure relates generally to non-invasive measurement of blood pressure. The measurement mechanism disclosed may be employed for determining various blood pressure related parameters for a subject that requires efficient hemodynamic monitoring. The subject is typically a mechanically ventilated patient treated in an intensive care unit (ICU), although the measurement may also be applied to spontaneously breathing patients, such as anesthetized patients. Blood pressure related parameters here refer to parameters or variables that may be derived from a blood pressure waveform signal.
Invasive blood pressure measurement is used when continuous tracking of blood pressure is required and when accurate information about the waveform of blood pressure is required. Invasive measurement of blood pressure is also used when an accurate or reliable insight of blood pressure cannot be obtained through non-invasive measurement methods. Invasive blood pressure measurement is therefore useful when brisk changes in the blood pressure are anticipated. Invasive blood pressure monitoring is required for the hemodynamic monitoring of mechanically ventilated patients and in connection with fluid therapy, for example.
Invasive blood pressure measurement is carried out with an intravascular cannulae by placing the needle of the cannulae in an artery. Compared to non-invasive techniques, invasive blood pressure measurements have therefore some drawbacks, which include the risk of infection, thrombosis, and bleeding. Patients with invasive blood pressure monitoring thus require more work and supervision than patients that do not require invasive measurement. Furthermore, non-invasive measurements are simpler to carry out and require less training of the nursing staff. However, the use of non-invasive methods is often not possible, due to the above clear advantages that the invasive methods have in providing accurate and continuous information about the blood pressure waveform.